Topical composition comprising a film-forming polymer for delivering an active ingredient to skin

ABSTRACT

A film-forming pharmaceutical composition for dermal application comprises at least one therapeutically active ingredient dissolved in a volatile solvent, the composition further comprising a film-forming polymer, a plasticizer and an oily release-enhancing agent. The composition is capable of forming, after application on skin and evaporation of the solvent, a continuous phase comprising the film-forming polymer and the plasticizer and a dispersed phase comprising droplets of the oily release-enhancing agent.

This application is a Divisional of co-pending patent application Ser. No. 14/410,489, filed on Dec. 22, 2014, which is the National Phase of PCT International Application No. PCT/EP2013/064301, filed on Jul. 5, 2013, which claims priority under 35 U.S.C. 119(e) to U.S. Provisional Application No. 61/668,846, filed on Jul. 6, 2012. The entire contents of all of the above applications are hereby incorporated by reference.

FIELD OF INVENTION

The present invention relates to a pharmaceutical composition for application on skin and containing a film-forming polymer and at least one active ingredient, the composition forming a thin and transparent two-phase film on the skin on evaporation of a solvent.

BACKGROUND OF THE INVENTION

Human skin, in particular the outer layer, the stratum corneum, provides an effective barrier against penetration of microbial pathogens and toxic chemicals. While this property of skin is generally beneficial, it complicates the dermal administration of pharmaceuticals in that a large quantity, if not most, of an active ingredient applied on the skin of a patient suffering from a dermal disease may not penetrate into the viable layers of the skin where it exerts its activity. To ensure an adequate penetration of the active ingredient into the dermis and epidermis, it is generally preferred to include the active ingredient in a dissolved state, typically in the presence of a low-molecular volatile solvent such as an alcohol, e.g. ethanol, or a diol, e.g. propylene glycol, which may also act as a penetration enhancer for the active ingredient. Another way to obtain penetration of the active ingredient into the skin is to provide occlusion by formulating the active ingredient in a hydrophobic vehicle such as petrolatum. However, ointments containing petrolatum generally have a tacky or greasy feel that persists for quite some time after application, and are consequently not cosmetically acceptable.

As an alternative to conventional formulations such as ointments, compositions containing film-forming polymers in which an active ingredient has been incorporated have been developed. Film-forming compositions have mainly been used to provide transdermal delivery of an active ingredient such as in transdermal patches or, more recently, as film-forming solutions composed of a film-forming polymer, a plasticiser and a low-molecular volatile solvent for the active ingredient. When the solution is applied on skin, a thin polymeric film is formed after evaporation of the solvent.

EP 515 312 B1 discloses a topical formulation containing terbinafine as the active ingredient and a film-forming polymer, e.g. polyvinylacetate or acrylic and methacrylic acid ester copolymers, for use as a nail varnish in the treatment of onchomycosis.

WO 2006/111426 discloses a film-forming solution containing a vitamin D derivative and a corticosteroid for use as a nail varnish in the treatment of nail psoriasis. The film-forming polymer may be selected from polyvinylpyrrolidone, butyl ester of polyvinyl methyl ether and maleic acid copolymer and acrylate and ammonium methacrylate copolymer. The composition may contain ethanol as a solvent and may additionally contain a penetration enhancer.

US 2007/0248658 discloses compositions comprising film-forming polyurethanes or polyurethane and acrylate copolymers and one or more active ingredients for use in dermal or transdermal delivery of the active ingredient(s) such as ethinylestradiol. The composition may additionally contain a low-molecular volatile solvent such as ethanol or isopropanol and a penetration enhancer such as oleic acid, oleyl alcohol, propylene glycol propylene carbonate, N-methylpyrrolidone and isopropyl myristate.

US 2004/0213744 discloses a sprayable composition for topical application comprising a film-forming polymer, a permeation enhancer, a solubilizer, a plasticizer and an active ingredient. The film-forming polymer may be an acrylic polymer or copolymer, a methacrylic acid polymer or copolymer, polyvinylacetate, polyvinyl alcohol, polyvinylpyrrolidone or a cellulose polymer. The permeation enhancer may be selected from surfactants, oleic acid, mixed esters of capric and caprylic acid, polyhydric alcohols, isopropyl myristate etc. The solubilizer may be a surfactant, polyhydric alcohol or a copolymer of dimethylamine ethyl methacrylate and methacrylic acid ester copolymer. The plasticizer may be selected from triethyl citrate, dimethyl isosorbide, acetyl tributyl citrate, castor oil, propylene glycol etc. The composition may further include a propellant, e.g. hydrocarbon, hydrofluorocarbon, dimethylether, nitrogen, carbon dioxide, etc.

WO 2007/031753 discloses a film-forming composition comprising an active ingredient which is present in at least 80% saturation, a film-forming polymer such as polyvinylpyrrolidone, polyvinyl alcohol, acrylic polymers and copolymers, methacrylic polymers and copolymers and cellulose polymers, a low-molecular volatile solvent such as ethanol, a propellant such as hydrofluoroalkane, and preferably also an antinucleating agent such as polyvinyl alcohol and a plasticizer such as glycerol, polyethylene glycol, oleic acid, citric acid, fatty acid esters, hydrocarbons etc.

An object of the present invention is to provide film-forming compositions that are thin and transparent so that they form a nearly invisible film on the skin, the film being flexible, fast drying and non-sticky.

Another object of the invention is to provide film-forming compositions that are capable of releasing an active ingredient incorporated therein over a prolonged period of time into the upper layers of the skin so that the composition may be administered less frequently than conventional topical compositions such as creams, ointments or gels.

A further object of the invention is to provide a composition in which the active ingredient is not significantly degraded, but remains chemically and physically stable throughout the shelf-life of the composition.

SUMMARY OF THE INVENTION

Film-forming compositions disclosed in the literature suffer from the drawback that only a minor proportion of the active ingredient incorporated therein is released from the composition. In the research leading to the present invention, we have surprisingly found that if an oily component is added to the film-forming solution, it is possible to obtain increased release over time of the active ingredient from the resulting film. Thus, it may be possible to obtain extended release of the active ingredient over a period of several days and consequently omit daily applications of a topical composition, which is currently the norm.

Accordingly, in one aspect the present invention relates to a film-forming pharmaceutical composition for dermal application, the composition comprising at least one therapeutically active ingredient dissolved in a pharmaceutically acceptable volatile solvent which is present in an amount of 50-99.5% w/w of the composition, the composition further comprising a film-forming polymer in an amount of 0.1-50% w/w, a plasticizer in an amount of 0.1-10% w/w, and an oily release-enhancing agent in an amount of 0.1-15% w/w;

the composition being capable of forming, after application on skin and evaporation of the solvent, a continuous phase comprising the film-forming polymer and the plasticizer and a dispersed phase comprising droplets of the oily release-enhancing agent.

In another aspect, the invention relates to a two-phase pharmaceutical composition comprising at least one therapeutically active ingredient, a continuous phase comprising a matrix formed from a film-forming polymer in an amount of 55-90% w/w of the dry composition and a plasticizer in an amount of 10-25% w/w of the dry composition, and a dispersed phase comprising droplets of an oily release-enhancing agent in an amount of 10-25% w/w of the dry composition, said two-phase composition being formed after application of the composition on skin and evaporation of a solvent.

Film-forming compositions of the invention have been found to form thin, transparent films when applied on skin. The compositions are virtually invisible and therefore more cosmetically acceptable to patients compared to visible patches. Furthermore, the film-forming compositions dry quickly and are not sticky, thus avoiding adhesion to the patients' clothing. When tested for substantivity, i.e. the ability to resist abrasion as a result of washing or general wear after application on skin, compositions including a hydrophobic film-forming polymer tend to exhibit increased substantivity on skin relative to compositions containing a hydrophilic film-forming polymer.

In the course of research leading to the invention, it was surprisingly found that the oily release-enhancing agent forms oil droplets in the film upon evaporation of the solvent (cf. Example 8 and 9 showing results of atomic force microscopy (AFM) measurements of film-forming compositions disclosed herein). Without being limited to any particular theory, it is assumed that the increased release obtained from film-forming compositions comprising an oily release-enhancing agent may be the result of diffusion of the active ingredient from the matrix of film-forming polymer and plasticizer into the oil droplets from which the active ingredient is released resulting in increased and continuous release from the film-forming composition. Furthermore, the oily release-enhancing agent may act as an emollient to improve hydration of the skin and control transepidermal water loss, thus reinforcing the occlusive effect of the film-forming polymer.

In a further aspect, the invention relates to a composition as disclosed herein for use in the treatment of dermal diseases and conditions.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows the release of betamethasone valerate (BMV) from a film-forming composition containing Klucel LF and 20% (by weight of the dry film-forming polymer) of the plasticizers TEC, TBC and DBS, or the oily release-enhancing agent MCT compared to the release of BMV from a film-forming composition containing no plasticizer or oily release-enhancing agent over a period of 72 hours.

FIG. 2 shows the release of BMV from a film-forming composition containing Eudragit RS PO and 20% (by weight of the dry film-forming polymer) of the plasticizers TEC, TBC and

DBS, or the oily release-enhancing agent MCT compared to the release of BMV from a film-forming composition containing no plasticizer or oily release-enhancing agent over a period of 72 hours.

FIG. 3 shows penetration of BMV from all three test compositions in the course of 24 hours.

FIG. 4 shows the concentration of betamethasone dipropionate (BDP) and its metabolite betamethasone in the skin of hairless rats after 1 day and 7.

FIG. 5 shows the serum concentration of betamethasone over 24 h from application on the skin of hairless rats of film-forming compositions and the comparative ointment.

FIG. 6 is a graph showing the amount of BDP released as a function of time from film-forming compositions containing Dermacryl 79 as the film-forming polymer or Dermacryl together with Arlamol E, Dermacryl together with Arlamol E and polysorbate 80 and Dermacryl together with Arlamol E, tributyl citrate and polysorbate 80.

FIG. 7 is a graph showing the amount of BMV released as a function of time from film-forming compositions containing Eudragit RS PO as the film-forming polymer, Eudragit RS PO together with tributyl citrate, Eudragit RS PO together with 20% (by weight of the dry film-forming polymer) medium chain triglycerides (MCT), Eudragit RS PO together with tributyl citrate and 20% (by weight of the dry film-forming polymer) MCT and Eudragit RS PO together with tributyl citrate and 40% (by weight of the dry film-forming polymer) MCT.

FIG. 8(a) is an image resulting from atomic force microscopy (AFM) of a film-forming composition comprising Eudragit RS PO as the film-forming polymer, FIG. 8(b) is an AFM image of a film-forming composition comprising Eudragit RS PO and triethyl citrate as the plasticizer, and FIG. 8(c) is an AFM image of a film-forming composition comprising Eudragit RS PO and MCT as the oily release-enhancing agent. The two-phase topography of the film including droplets of the oil is clearly visible in FIG. 8(c). FIG. 8(d) i-iii show AFM images obtained by applying varying forces to the sample surface using the AFM probe tip (the sample being a film containing Eudragit RS PO with 20% MCT) i) initial force applied, ii) 5× initial force applied, iii) 17× initial force applied.

FIG. 9 is an image resulting from AFM of a film-forming composition comprising Eudragit RS PO as the film-forming polymer, tributyl citrate as the plasticizer and MCT as the oily release-enhancing agent. The two-phase topography of the film including droplets of the MCT is clearly visible in the figure.

DETAILED DISCLOSURE OF THE INVENTION

Definitions

The term “vitamin D derivative” is intended to indicate a biologically active metabolite of vitamin D₃, such as calcitriol, or a precursor to such a metabolite, such as alfacalcidol.

The term “vitamin D analogue” is intended to indicate a synthetic compound comprising a vitamin D scaffold with sidechain modifications and/or modifications of the scaffold itself. The analogue exhibits a biological activity on the vitamin D receptor comparable to that of naturally occurring vitamin D compounds.

“Calcipotriol” is a vitamin D analogue of the formula

Calcipotriol has been found to exist in two crystalline forms, an anhydrate and a monohydrate. Calcipotriol monohydrate and its preparation are disclosed in WO 94/15912.

The term “storage stability” or “storage stable” is intended to indicate that the composition exhibits chemical and physical stability characteristics that permit storage of the composition for a sufficient period of time at refrigeration or, preferably, room temperature to make the composition commercially viable, such as at least 12 months, in particular at least 18 months, and preferably at least 2 years.

The term “chemical stability” or “chemically stable” is intended to mean that no more than 10%, preferably no more than 6%, of the active ingredients degrades over the shelf-life of the product, typically 2 years, at room temperature. An approximation of chemical stability at room temperature is obtained by subjecting the composition to accelerated stability studies at 40° C. where the composition is placed in a heating cupboard at 40° C. and samples are taken at 1, 2 and 3 months and tested for the presence of degradation products by HPLC. If less than about 10% of the substance has degraded after 3 months at 40° C., this is usually taken to correspond to a shelf-life of 2 years at room temperature. When the active ingredient included in the composition is calcipotriol, “chemical stability” usually indicates that the calcipotriol does not degrade significantly over time to 24-epi calcipotriol or other degradation products of calcipotriol in the finished pharmaceutical product.

The term “physical stability” or “physically stable” is intended to mean that the active ingredients do not precipitate from the vehicle phase throughout the shelf life of the composition.

The term “substantially anhydrous” is intended to mean that the content of free water in the ointment composition does not exceed about 2% by weight, preferably not about 1% by weight, of the composition.

The term “medium-chain triglycerides” is used to indicate triglyceride esters of fatty acids with a chain length of 6-12 carbon atoms. A currently favoured example of such medium chain triglycerides is a mixture of caprylic (C₈) and capric (C₁₀) triglycerides, e.g. available under the trade name Miglyol 812.

The term “skin penetration” is intended to mean the diffusion of the active ingredient into the different layers of the skin, i.e. the stratum corneum, epidermis and dermis.

The term “skin permeation” is intended to mean the flux of the active ingredient through the skin into the systemic circulation or the receptor fluid of the Franz cell apparatus used in the experiment.

The term “release” is intended to indicate the amount of active ingredient leaving the composition when it is applied on a surface, e.g. a silicone membrane. The in vitro release through the membrane may be determined by the method disclosed in Example 2. In this context, the term “extended release” is intended to mean that the release of the active ingredient takes place over a period of at least 48 hours, such as at least 72 hours. The term “increased release” is intended to indicate that the total amount of active ingredient released over time is increased from a film-forming composition containing both a plasticizer and an oily release-enhancing agent compared to a film-forming composition containing the film-forming polymer alone or together with a plasticizer, but not together with an oily release-enhancing agent.

The term “dry composition” is intended to indicate the polymeric film formed upon application of the film-forming composition as defined herein on the skin and evaporation of volatile components such as a solvent.

Embodiments

In the present composition, the film-forming polymer may be selected from the group consisting of cellulose derivatives, acrylic polymers, acrylic copolymers, methacrylate polymers, methacrylate copolymers, polyurethanes, polyvinylalcohol or a derivative thereof such as polyvinylacetate, silicone polymers and silicone copolymers, and copolymers thereof.

When the film-forming polymer is a cellulose derivative, it may be selected from the group consisting of ethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropylmethyl cellulose.

When the film-forming polymer is an acrylic polymer, it may be selected from the group consisting of methyl methacrylate and butyl methacrylate copolymer, ethyl acrylate and methyl methacrylate copolymer, acrylate and ammonium methacrylate copolymer type A and type B, and acrylates/octylacrylamide copolymer.

The film-forming polymer may suitably be present in an amount of 5-20% w/w such as 10-15% w/w of the composition.

In the present composition, the plasticizer may be selected from the group consisting of triethyl citrate, tributyl citrate, acetyl triethyl citrate, triacetin, dibutyl sebacate and polyethylene glycol 100-1000, e.g. polyethylene glycol 400.

Incorporation of a plasticizer in the film-forming composition decreases the glass transition temperature (Tg) of the film-forming polymer. Tg is an indirect indicator of film flexibility as the polymeric film is flexible at temperatures below Tg. Thus, Tg values below skin temperature indicates that the film is flexible on skin. In a specific embodiment, a decreased Tg has been obtained for film-forming compositions containing an acrylic polymer as the film-forming polymer and triethyl citrate as the plasticizer.

The plasticizer may suitably be present in an amount of 2-5% w/w of the composition.

The oily release-enhancing agent may be selected from the group consisting of

(a) a polyoxypropylene fatty alkyl ether;

(b) an isopropyl ester of a straight or branched chain C₁₀₋₁₈ alkanoic or alkenoic acid;

(c) a propylene glycol mono- or diester of a C₈₋₁₄ fatty acid;

(d) a straight or branched C₈₋₂₄ alkanol or alkenol;

(e) a C₆₋₂₂ acylglyceride;

(f) N-alkylpyrrolidone or N-alkylpiperidone; and

(g) a mineral oil such as liquid paraffin.

When the oily release-enhancing agent is a polyoxypropylene fatty alkyl ether, it may be selected from the group consisting of polyoxypropylene-15-stearyl ether, polyoxypropylene-11-stearyl ether, polyoxypropylene-14-butyl ether, polyoxypropylene-10-cetyl ether or polyoxypropylene-3-myristyl ether.

When the oily release-enhancing agent is an isopropyl ester of a straight or branched chain C₁₀₋₁₈ alkanoic or alkenoic acid, it may be selected from the group consisting of isopropyl myristate, isopropyl palmitate, isopropyl isostearate, isopropyl linolate or isopropyl monooleate.

When the oily release-enhancing agent is a propylene glycol monoester of a C₈₋₁₄ fatty acid, it may be propylene glycol monolaurate or propylene glycol monocaprylate, and when it is a propylene glycol diester of a C₈₋₁₄ fatty acid, it may be propylene glycol dipelargonate.

When the oily release-enhancing agent is a straight C₈₋₂₄ alkanol, it may be capryl, lauryl, cetyl, stearyl, oleyl, linoelyl or myristyl alcohol, or when it is a branched C₈₋₂₄ alkanol it may be a branched C₁₈₋₂₄ alkanol such as 2-octyldodecanol.

When the oily release-enhancing agent is a C₆₋₂₂ acylglyceride, it may be a vegetable oil, e.g. sesame oil, sunflower oil, palm kernel oil, corn oil, safflower oil, olive oil, avocado oil, jojoba oil, grape kernel oil, canola oil, wheat germ oil, almond oil, cottonseed oil, peanut oil, walnut oil or soybean oil, a highly purified vegetable oil, e.g. medium chain triglycerides (caprylic/capric triglycerides), long chain triglycerides, castor oil, caprylic monoglyceride, caprylic/capric mono- and diglycerides or caprylic/capric mono-, di- and triglycerides.

The oily release-enhancing agent may suitably be present in an amount of 1-10% w/w such as 2-6% w/w of the composition.

The present composition comprises a volatile solvent which may be a low-molecular solvent, e.g. a lower alcohol such as methanol, ethanol, isopropanol or butanol, a C₁₋₄ ester of a C₁₋₄ carboxylic acid such as methyl acetate, ethyl acetate, butyl acetate, methyl formate or propyl propionate, acetone, or a volatile silicone oil such as cyclomethicone, dimethicone or hexamethyldisiloxane.

The composition may comprise a low amount (e.g. of water acting as an additional plasticizer or co-solvent. It is, however, currently preferred that the composition is substantially anhydrous.

To reduce or delay crystallisation of the active ingredient in the applied, dry film-forming composition, it may be an advantage to include an anti-nucleating agent. The anti-nucleating agent may suitably be selected from polymers such as polyvinyl alcohol, hydroxypropyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose and carboxymethyl cellulose.

The active ingredient included in the present film-forming composition may suitably be selected from the group consisting of vitamin D derivatives or analogues, corticosteroids, phosphodiesterase 4 inhibitors, ingenol derivatives, retinoids such as adapalene, JAK inhibitors, NK-1 receptor antagonists, calcineurin inhibitors such as tacrolimus or pimecrolimus, keratolytic agents such as salicylic acid or lactic acid, antibiotics such as fusidic acid or clindamycin, non-steroidal antiinflammatory agents and local anesthetics such as lidocain.

The vitamin D derivative or analogue may be selected from calcipotriol, calcitriol, tacalcitol, maxacalcitol, paricalcitol and alfacalcidol. A preferred vitamin D analogue which has been shown to be effective in the treatment of psoriasis is calcipotriol. Before dissolution in the solvent, calcipotriol may be in the form of anhydrate or monohydrate, preferably the monohydrate.

The corticosteroid may be selected from the group consisting of amcinonide, betamethasone, budenoside, clobetasol, clobetasone, cortisone, desonide, desoxycortisone, desoximethasone, dexamethasone, diflucortolon, diflorasone, flucortisone, flumethasone, flunisolide, fluocinonide, fluocinolon, fluorometholone, fluprednisolone, flurandrenolide, fluticasone, halcinonide, halobetasol, hydrocortisone, meprednisone, methylprednisone, mometasone, paramethasone, prednicarbate, prednisone, prednisolone and triamcinolone or a pharmaceutically acceptable ester or acetonide thereof. The corticosteroid may preferably be selected from betamethasone, budenoside, clobetasol, clobetasone, desoximethasone, diflucortolon, diflorasone, fluocinonide, fluocinolon, halcinonide, halobetasol, hydrocortisone, mometasone and triamcinolone or a pharmaceutically acceptable ester thereof. The corticosteroid ester may for instance be betamethasone acetate, betamethasone dipropionate, betamethasone valerate, clobetasol propionate, dexamethasone acetate, flumethasone pivalate, fluticasone propionate, hydrocortisone acetate, hydrocortisone butyrate or mometasone furoate. The acetonide may be selected from fluocinolone acetonide or triamcinolone acetonide. The corticosteroid is preferably betamethasone dipropionate or betamethasone valerate.

In a currently favoured embodiment, the composition comprises calcipotriol or calcipotriol monohydrate as the vitamin D analogue and betamethasone valerate or betamethasone dipropionate as the corticosteroid.

The phosphodiesterase 4 inhibitor may for instance be selected from the compounds disclosed in WO 2008/077404, WO 2008/104175, WO 2008/128538 or WO 2010/069322 the disclosure of which is included herein by reference.

The ingenol derivative may suitably be selected from the group consisting of ingenol-3-angelate, ingenol-5-angelate, ingenol-20-angelate, 20-O-acetyl-ingenol-3-angelate and 20-deoxy-ingenol-3-angelate. Ingenol-3-angelate, also known as ingenol-3-mebutate or PEP 005, has recently been approved in the US and EU for the treatment of actinic keratosis.

In a specific embodiment, the invention relates to a film-forming composition comprising a therapeutically active ingredient and

Acrylates/ammonium methacrylate copolymer 10-15% w/w Medium chain triglycerides 3-6% w/w Tributyl citrate 2-3% w/w Ethanol, anhydrous 75-80% w/w

-   -   In another specific embodiment, the invention relates to a         film-forming composition comprising a therapeutically active         ingredient and

Acrylates/octacrylamide copolymer 10-15% w/w Polypropylene glycol 11 stearyl ether 1.5-3% w/w Tributyl citrate 2-3% w/w Ethanol, anhydrous 80-90% w/w

The present composition may also comprise other components commonly used in dermal formulations, e.g. antioxidants (e.g. alpha-tocopherol), preservatives, pigments, emollients, skin soothing agents, skin healing agents and skin conditioning agents such as urea, glycerol, allantoin or bisabolol, cf. CTFA Cosmetic Ingredients Handbook, 2^(nd) Ed., 1992. In a favoured embodiment, the composition may comprise an anti-irritative agent such as menthol, eucalyptol or nicotinamide.

The composition of the invention may be used in the treatment of psoriasis, sebopsoriasis, pustulosis palmoplantaris, atopic dermatitis, contact dermatitis, eczema, actinic keratosis, basal cell carcinoma, squamous cell carcinoma, pruritus, ichtyosis, rosacea and acne and related skin diseases by topically administering an effective amount of a composition according to the invention to a patient in need of such treatment. Said method preferably comprises topical administration once or twice a day of a therapeutically sufficient dosage of said composition. To that end, the composition according to the invention preferably contains about 0.0001-1% w/w of the active ingredient. It is envisaged that the present composition may advantageously be used for maintenance treatment of these dermal diseases, i.e. continued treatment after the disappearance of visible symptoms of the disease in order to delay recurrence of the symptoms. The present composition has the added advantage for the treatment of skin diseases involving dry or flaky skin, e.g. psoriasis, that the oily release-enhancing agent acts as an emollient hydrating and softening the flaky skin to give the skin a less dry appearance.

The composition according to the invention may be applied by spreading, painting, brushing or dabbing. In a currently favoured embodiment, the composition may be dispensed as a spray from a container, typically of the type comprising a container body and valve assembly. The container body may, for instance, comprise a plastic, glass or metal body which may be lined with an chemically inert coating material to avoid degradation of the composition due to interaction between the body material and the composition. The valve assembly may comprise a valve body or housing provided with a valve stem, a spring, a dip tube, an actuator and a nozzle. The valve body may be provided with a pump connected to the dip tube. The pump comprises a piston, a cylinder, a one-way valve and a nozzle. When the pump is activated on pressing the actuator, it forces the piston into the cylinder, which forces the composition through the nozzle. When the actuator is released, the piston moves back, pulling a portion of the composition back into the cylinder; this is forced out of the nozzle the next time the actuator is pressed. A one-way valve at the bottom of the pump only allows the composition to flow up the dip tube into the pump, not back into the container. Spray container nozzles also have a one-way valve in them that keeps air from flowing back into the pump and allows for suction within the pump so that the composition can be pulled up the dip tube.

The valve assembly may comprise a metering valve to permit only a metered quantity of the composition to be dispensed with each actuation of the actuator.

For storage, safety and/or hygiene reasons, the actuator may be provided with an protective hood or overcap, separate or integral therewith. The actuator itself may comprise a simple button actuator, or may for example comprise a flip-top or twist-lock.

The inclusion of a tamper-evidence tab, which has to be broken before first use of the pump spray container, is desirable.

The film-forming composition of the invention may also be applied from a bag-on-valve dual compartment packaging system. The principle behind the bag-on-valve system is that a flexible bag typically in a rolled-up configuration is mounted to the valve of an aerosol can containing a propellant such as compressed air or nitrogen. The composition is filled into the bag and then the propellant is filled into the aerosol can between the inner wall of the can and the outer wall of the bag. When the valve is actuated the propellant forces the product out of the bag and into the environment. This configuration ensures that the product is not in contact with the propellant.

The invention is further illustrated by the following examples which are not in any way intended to limit the scope of the invention as claimed.

EXAMPLES Example 1

Compositions

Reference compositions were prepared including the following ingredients.

Plasticizer Oil Solvent Polymer TEC TBC DBS PEG MCT Ethanol Klucel LF 5% X X X X X X Eudragit E 15% X X Eudragit RS 15% X X X X X Dermacryl 79 10% X X X Dermacryl 79 + Klucel LF X X TEC: triethyl citrate TBC: tributyl citrate DBS: dibutyl sebacate PEG: polyehtylene glycol 400 MCT: medium chain triglycerides

The content of plasticizer and/or oil in the compositions was 20% by weight of the dry film-forming polymer. In addition, 1.2% by weight of betamethasone valerate (1% by weight betamethasone) was added to the compositions.

To prepare the compositions, BMV, plasticizer or oily release-enhancing agent (MCT) were dissolved in the solvent by stirring for 1-2 hours. The film-forming polymer was added slowly with stirring, and the resulting mixture was stirred overnight to complete the dissolution of the polymer.

Example 2

Compositions

Ingredients (mg/g) 01A 02A 03A 04A Betamethasone diproprionate 12.86 12.86 12.86 12.86 Acrylates/octylacrylamide 100 100 100 100 copolymer (Dermacryl 79) PPG-11 stearyl ether (Arlamol 20 20 20 E) Polysorbate 80 2 2 Tributyl citrate 20 Ethanol, anhydrous 887.14 867.14 865.14 845.14

Composition 04A is a composition according to the invention, while compositions 01A, 02A and 03A are reference compositions.

To prepare the compositions, BDP, plasticizer, oily release-enhancing agent (Arlamol E) (as appropriate) and polysorbate 80 (as appropriate) were dissolved in the solvent by stirring for 1-2 hours. The film-forming polymer was added slowly with stirring, and the resulting mixture was stirred overnight to complete the dissolution of the polymer.

Compositions according to the invention

Ingredients (mg/g) 05A 06A 06P Betamethasone valerate 12.14 12.14 Eudragit RS PO 150 150 150 Medium chain triglyceride 30 60 60 Tributyl citrate 30 30 30 Ethanol, anhydrous 777.9 747.9 760

To prepare the compositions, BMV, plasticizer and oily release-enhancing agent (MCT) were dissolved in the solvent by stirring for 1-2 hours. The film-forming polymer was added slowly with stirring, and the resulting mixture was stirred overnight to complete the dissolution of the polymer.

Example 3 In Vitro Release Testing of Compositions of Example 1

The purpose of the study is to explore the effect of polymer and plasticizer or oily release-enhancing agent on the in vitro release of Betamethasone-17-valerate (BMV) from compositions according to Example 1, with a view to optimising the type and concentration of polymer and plasticizer with regard to obtaining a prolonged release profile. This is done by testing various types and concentrations of polymers and plasticizers, as these are parameters expected to affect drug release from the polymeric in situ forming films.

Membrane:

Dow Corning® 7-4107 Silicone Elastomer Membrane, 75 μm.

Diffusion Cell System:

Modified dialysis cells (LEO Pharma, Denmark).

Receptor compartment: ˜1.5 ml. The actual volume of each cell is registered by weighing of the assembled cell before and after filling of the receptor compartment.

Diameter: ˜1.55 cm, corresponding to an available diffusion area of 1.89 cm².

Sheets of silicone membrane are cut to size (circles, Ø=22 mm). The membrane is placed between the two compartments of the dialysis cells with the glossy side facing the donor compartment.

The receptor compartment is filled with preheated receptor medium (the actual volume of each cell is registered by weighing) and possible air bubbles removed. The sampling arm is sealed with a plastic bung and/or parafilm to prevent evaporation of the receptor medium. Uniform mixing of the receptor phase is obtained with a magnetic bar placed in the receptor compartment. The diffusion cells are placed in a heating cabinet set at ˜37° C. to maintain a temperature of ˜32° C. at the membrane surface. The stirring bed is set at 300 rpm. The cells are allowed to equilibrate for minimum 30 min before application of FFS and thus start of experiment.

Receptor Medium: 10% w/w methyl-β-cyclodextrin in 0.1M acetate buffer pH 4.5. The receptor medium is degassed in an ultrasound water bath for 20 minutes prior to the start of the experiment and before 24 h and 48 h sampling. It was ensured that sink conditions were present at all times during the study period; i.e. that the concentration of the drug compounds in the recipient phase was below 10% of the solubility of the drug substances in the medium.

Application, Occlusion, Dosage and Volume of Test Formulation:

240 μl film-forming composition (FFC) is gently applied and distributed on the membrane surface (t=0 h) using an eppendorf pipette. The pipette is not tared before application as previous experiments showed no significant retention of formulation. This may partly be a consequence of solvent evaporation complicating the registration of possible formulation retention. The weight of 240 μl FFC is registered to be used in the data processing of the release results. The actual volume of FFC delivered by an eppendorf pipette may vary as a consequence of the varying viscosity of the FFC. Therefore, the weight of 10 consecutive applications of 240 μl FFC (the corresponding placebo formulation is used for this purpose) is registered, an average calculated and used in the data processing of the release results.

After application of FFC the dialysis cell is placed back on the stirring bed. The cell is placed with the membrane horizontally to obtain an even distribution of FFC during solvent evaporation/film formation by hindering of accumulation of the FFC/film in the bottom of the donor compartment.

Exposure and Sampling Times:

Samples of 1500 μl (the actual volume is weighed and registered) are withdrawn from each cell at regular time intervals. After each sampling the receptor compartment is refilled with preheated fresh receptor medium. The withdrawn samples are stored in sealed HPLC vials at 2-8° C. and protected from light until quantification by HPLC analysis. Sampling time points: 0, 1, 6, 24, 30, 48, 54, 72 h.

Study Design:

Each formulation is tested in 3 replicates (n=3).

HPLC Analysis:

HPLC analysis in New Products, Analytical department according to protocol 130-FKFT-20110614A.

Data Analysis:

The analytically determined BMV assay values were correspondingly corrected for the replenishments. The drug concentrations are transferred to a spread sheet (Excel) to calculate the cumulative amount released over the period of 0 to 72 h. The release rate is calculated from the linear part of the curve of the cumulative amount released versus square root of time. Based on the data of all individual cells in a group, the mean value and the standard deviation (SD) are calculated for each group.

Results

The results appear from FIGS. 1 and 2.

FIG. 1 shows the release of BMV from a film-forming composition containing Klucel LF and 20% (by weight of the dry film-forming polymer) of the plasticizers TEC, TBC and DBS, or the oily release-enhancing agent MCT compared to the release of BMV from a film-forming composition containing no plasticizer or oily release-enhancing agent over a period of 72 hours. It appears from FIG. 1 that the inclusion of a plasticizer or oily release-enhancing agent results in a significant increase in the release of active ingredient from the film.

FIG. 2 shows the release of BMV from a film-forming composition containing Eudragit RS PO and 20% (by weight of the dry film-forming polymer) of the plasticizers TEC, TBC and DBS, or the oily release-enhancing agent MCT compared to the release of BMV from a film-forming composition containing no plasticizer or oily release-enhancing agent over a period of 72 hours. It appears from FIG. 2 that the inclusion of a plasticizer or oily release-enhancing agent results in a significant increase in the release of active ingredient from the film.

Example 4 In Vitro Release Testing of Compositions of Example 2

The purpose of the study is to explore the effect of the film-forming polymer, plasticizer and oily release-enhancing agent on the in vitro release of betamethasone-17-valerate (BMV) and betamethasone dipropionate (BDP) from compositions according to Example 2, with a view to optimising the type and concentration of polymer and oily release-enhancing agent with regard to obtaining a prolonged release profile.

Membrane:

Dow Corning® 7-4107 Silicone Elastomer Membrane, 75 μm.

Diffusion Cell System:

Modified dialysis cells (LEO Pharma, Denmark).

Receptor compartment: ˜1.5 ml. The actual volume of each cell is registered by weighing of the assembled cell before and after filling of the receptor compartment.

Diameter: ˜1.55 cm, corresponding to an available diffusion area of 1.89 cm².

Sheets of silicone membrane are cut to size (circles, Ø=22 mm). The membrane is placed between the two compartments of the dialysis cells with the glossy side facing the donor compartment.

The receptor compartment is filled with preheated and degassed receptor medium (the actual volume of each cell is registered by weighing) and possible air bubbles removed. The sampling arm is sealed with a plastic bung and parafilm to prevent evaporation of the receptor medium. Uniform mixing of the receptor phase is obtained with a magnetic bar placed in the receptor compartment. The diffusion cells are placed in a heating cabinet set at ˜37° C. to maintain a temperature of ˜32° C. at the membrane surface. The stirring bed is set at 300 rpm. The cells are allowed to equilibrate for minimum 30 min before application of FFS and thus start of experiment.

Receptor Medium:

10% w/w methyl-β-cyclodextrin in 0.05M acetate buffer pH 4.0. The receptor medium is degassed in an ultrasound water bath for minimum 20 minutes prior to the start of the experiment and before 24 h and 48 h sampling. It was ensured that sink conditions were present at all times during the study period; i.e. that the concentration of the drug compounds in the recipient phase was below 10% of the solubility of the drug substances in the medium.

Acetate Buffer

Excipient (g/L) Function Acetic acid, glacial 2.567 Buffer Sodium acetate trihydrate 0.988 Buffer Methyl-β-cyclodextrin 100 Solubilising agent Purified water Ad 1 L Solvent NaOH/HCl ad pH 4.0

Preparation of Acetate Buffer

Mix all the excipients. Adjust the pH with either NaOH or HCI to obtain a pH of 4.0. Store the buffer at 5° C. until use.

Application, Occlusion, Dosage and Volume of Test Formulation:

240 μl film-forming composition is gently applied and distributed on the membrane surface (t=0 h) using a Gilson pipette. The pipette is not tared before or weighed after application of composition as previous experiments showed no significant retention of composition. This may partly be a consequence of solvent evaporation complicating the registration of possible formulation residue. The weight of 240 μl film-forming composition is registered to be used in the data processing of the release results.

After application of composition the dialysis cell is placed back on the stirring bed in the heating cabinet. The cell is placed with the membrane horizontally to obtain an even distribution of the film-forming composition during solvent evaporation/film formation, thereby hindering accumulation of the film in the bottom of the donor compartment.

Exposure and Sampling Times:

Samples of 1500 μl (the actual volume is weighed and registered) are withdrawn from each cell at regular time intervals. After each sampling the receptor compartment is refilled (the exact same volume as withdrawn!) with preheated fresh receptor medium.

The withdrawn samples are stored in sealed HPLC vials at 2-8° C. and protected from light until quantification by HPLC analysis at the end of the experiment.

Sampling time points: 0, 1, 6, 24, 30, 48, 54 h.

Study Design:

Each formulation is tested in 3 replicates (n=3).

BDP recovery: After ended experiment the remaining film is recovered (as much of the film as possible is scrape off the sides of the donor compartment) and re-dissolved in 5.0 ml absolute ethanol.

Results

The accumulated amount of released BDP (%) from Dermacryl 79 films is shown in FIG. 6. The data indicates that the lowest release is obtained from the composition containing only the film-forming polymer whereas the addition of Arlamol E increases the release and combining the plasticiser tributyl citrate and polysorbate 80 with Arlamol E further increases the release. Adding the surfactant polysorbate 80 to the formulation containing Arlamol E seems to slow down the release rate of BDP.

FIG. 7 shows the accumulated amount of BMV released (%) from Eudragit RS PO films. The results indicate that the lowest release is obtained from compositions containing only the film-forming polymer whereas the addition of tributyl citrate or MCT separately increases the release. The release of BMV is increased further from film-forming compositions containing both tributyl citrate and either 20% (w/w dry weight of the film) or 40% MCT. It further appears that the amount of active ingredient released from the compositions may be adjusted by modifying the concentration of MCT in the compositions.

Example 5

Skin Substantivity Testing

Topical substantivity of film-forming compositions according to Example 1 is tested by applying film-forming compositions including a colour additive (curcumin) in an amount of 1 mg/g on excised pig ear skin and determining the ΔE value before and after the film has been washed and dried. The ΔE value is a measure of the difference in skin colour before and after washing and drying. Thus, a substantive film results in a low ΔE value, preferably close to zero.

5% Klucel LF FFS/20% MCT:

-   -   ΔE (start→1. Wash/dry)=38     -   ΔE (start→2. Wash/dry)=42

15% Eudragit RS PO FFS/20% MCT:

-   -   ΔE (start→1. Wash/dry)=0.1     -   ΔE (start→2. Wash/dry)=1.2

10% Dermacryl 79 FFS/20% MCT:

-   -   ΔE (start→1. Wash/dry)=0.9     -   ΔE (start→2. Wash/dry)=1.5     -   →Klucel<Dermacryl˜Eudragit     -   The difference in substantivity can be ascribed to the         water-solubility of the film-forming polymer used in the         composition → the hydrophilic Klucel film-forming composition is         very easily washed off, i.e. has a very poor substantivity.

Example 6

In Vitro Skin Penetration

To investigate the skin penetration and permeation of BMV from compositions according to example 1, a skin diffusion experiment was conducted. Full thickness skin from pig ears was used in the study. The skin was cleaned and kept frozen at −18° C. before use. On the day prior to the experiment the skin was placed in a refrigerator (5±3° C.) for slow defrosting.

Static Franz-type diffusion cells with an available diffusion area of 3.14 cm² and receptor volumes ranging from 8.6 to 11.1 ml were used in substantially the manner described by T. J. Franz, “The finite dose technique as a valid in vitro model for the study of percutaneous absorption in man”, in Current Problems in Dermatology, 1978, J. W. H. Mall (Ed.), Karger, Basel, pp. 58-68. The specific volume was measured and registered for each cell. A magnetic bar was placed in the receptor compartment of each cell. After mounting the skin, physiological saline (35° C.) was filled into each receptor chamber for hydration of the skin. The cells were placed in a thermally controlled water bath which was placed on a magnetic stirrer set at 300 rpm. The circulating water in the water baths was kept at 35±1° C. resulting in a temperature of about 32° C. on the skin surface. After 30 min the saline was replaced by the receptor medium, 15 mM isotonic acetate buffer, pH 5.5, containing 1% methyl-β-cyclodextrin. Sink conditions were maintained at all times during the period of the study, i.e. the concentration of the active compound in the receptor medium was below 10% of the solubility of the compound in the medium.

The in vitro skin permeation of each test composition containing ³H-BMV was tested in 6 replicates (i.e. n=6). Each test composition was applied on the skin membrane at 0 hours using a pipette.

The skin penetration experiment was allowed to proceed for 24 hours. Samples were then collected from the following compartments at 2, 6 and 24 h (only the receptor medium was sampled at 24 h):

The remaining film was removed, and the stratum corneum was collected by tape stripping once using up to 15 D-Squame® tape discs (diameter 22 mm, CuDerm Corp., Dallas, Tex., USA). Each tape disc is applied to the test area using a standard pressure for 10 seconds and removed from the test area in one gentle, continuous move. For each repeated strip, the direction of tearing off was varied. The viable epidermis and dermis was then sampled from the skin in a similar fashion.

Samples (1 ml) of the receptor fluid remaining in the diffusion cell were collected and analysed.

The concentration of ³H-BMV in the samples were determined by liquid scintillation counting.

The results appear from FIG. 3 below showing that in the course of 21 hours BMV penetrated from all three test compositions, and that the BMV mainly accumulated in the stratum corneum rather than in the epidermis. More of the BMV penetrated from the Klucel LF composition containing 20% (by weight of dry film-forming polymer) MCT than from the Klucel LF composition without plasticizer or oily release-enhancing agent. None of the BMV permeated into the receptor medium.

Example 7

In Vivo Skin Penetration

Compositions similar to those described in Example 1, but containing betamethasone dipropionate (BDP; 0.643 mg/g) as the active ingredient and Dermacryl 79, DynamX and Eudragit RL PO as the film-forming polymers are investigated for penetration into the skin of hairless rats over a period of 7 days. A betamethasone ointment (purple) is used as a comparative formulation.

Male hairless rats of the OFA-hr/hr strain are obtained from Charles River, USA.

The rats are weighed prior to study initiation. Under isofluorane anesthesia, 100 μl of formulation is applied to a 4×3 cm area on the back of each rat. The rat is left for 2 minutes to permit the formulation to dry, and an Optiskin film (5.3×7.2 cm, URGO Laboratories, France) is applied over the area and on top of that, Fixomull stretch (BSN Medical, Germany).

Sublingual blood samples are collected from the animals in each group to be terminated 24 h post dosing. The samples are drawn 30 min, 2 h, 4 h and 6 h post dosing.

Animals are terminated at either 24 h or 7 days post dosing. Sublingual blood samples are collected from each animal prior to termination. The rats are euthanized with CO₂. Skin biopsies are taken from the applied skin area. The skin is cleaned gently with a tissue soaked in 99.9% ethanol. The biopsies are weighed and kept at −80° until quantitative analysis.

The concentration of BDP or betamethasone in the samples is determined by LC mass spectrometry.

The results appear from FIGS. 4 and 5 below.

FIG. 4 shows the skin concentration of BDP and its metabolite betamethasone after 1 day and 7 from which it appears that the skin penetration after one day is highest from a film-forming composition containing DynamX as the film-forming polymer, and that application of film-forming compositions containing DynamX or Eudragit RL PO as the film-forming polymer results in higher penetration of the active ingredient that when the comparative ointment is applied. In further appears that BDP and/or betamethasone remains in the skin for 7 days after application of a film-forming composition containing Dermacryl 79 or DynamX.

FIG. 5 shows the serum concentration of betamethasone over 24 h from application of the film-forming compositions and the comparative ointment. It appears that application of the ointment leads to permeation through the skin, whereas hardly any betamethasone is found in serum after application of the film-forming compositions.

Example 8 Atomic Force Microscopy Imaging of Film-Forming Compositions of Example 1

AFM imaging was performed on film-forming compositions comprising Eudragit RS PO as the film-forming polymer and either triethyl citrate as the plasticizer or MCT as the oily release-enhancing agent.

AFM samples were produced by depositing 20 μL of film-forming composition onto a glass slide which had been cleaned with acetone and isopropanol. The film was left for 22 hours to dry on a hot plate at 30° C. Samples small enough for AFM measurements were then produced by dividing the glass slide supporting the film into sections approximately 0.8×0.8 cm². For AFM measurements, samples were mounted onto AFM stubs. These stubs are metallic discs, approximately 1 cm in diameter, which are held magnetically to the AFM sample stage.

AFM Measurements

AFM measurements were carried out using a Multimode Scanning Probe Microscope (Veeco) with a Nanoscope IIIA controller and Nanoscope software (Version 7.341). Imaging was performed in tapping mode in ambient conditions. Tapping mode images are obtained by oscillating the AFM cantilever at a frequency close to its resonant frequency. As the probe is brought down to the sample surface, the amplitude of the cantilever oscillation is altered by forces between the probe tip and the sample. The probe tip taps the sample surface every oscillation. A feedback system causes the height of the AFM cantilever above the sample surface to change such that the amplitude of oscillation remains constant. It is this change in cantilever vertical position that produces a topographical AFM image. This method is further described by Zhong et al [Zhong, Q., et al., Fractured Polymer Silica Fiber Surface Studied by Tapping Mode Atomic-Force Microscopy. Surface Science, 1993. 290(1-2): p. L688-L692.)

‘All in One’ AFM probes (AIOAI, Budget Sensors) were used for both imaging and nanoindentation. The probes have spring constants between 0.2 N/m and 40 N/m. Accurate determination of the spring constants for each AFM probe used in these experiments was carried out using the Sader method [Sader, J. E., J. W. M. Chon, and P. Mulvaney, Calibration of rectangular atomic force microscope cantilevers. Review of Scientific Instruments, 1999. 70(10): p. 3967-3969.)

The probes have resonant frequencies from 15 to 350 kHz. AFM images were analysed using Nanoscope Analysis (Version 1.3, Bruker).

For interpretation of nanoindentation data, it is important that the tip extremity has a spherical shape. When this is not the case, the shape of the tip can be corrected using Electron Beam Induced Deposition (EBID). This technique allows a perfect spherical apex to be formed by depositing amorphous carbon deposits onto the AFM tip [Beard, J. D., S. N. Gordeev, and R. H. Guy, AFM Nanotools for Surgery of Biological Cells. Journal of Physics: Conference Series, 2011. 286: p. 012003.1. The probe tips were imaged using Scanning Electron Microscopy (SEM) (6301F, JEOL) and the radius of curvature was measured. Probes were mounted onto sample holders which could support the AFM probes at 45° to the horizontal. By supporting the AFM tips in this way, both the dimensions of the cantilever and the probe tip radius could be measured.

Indentation was performed in contact mode. In contact mode, the AFM probe tip is kept in constant contact with the sample surface. Indentation parameters, such as the approach rate and surface delay must be carefully chosen to get reliable results. These were specified prior to indentation in the Nanoscope software. The software measured the deflection of the AFM cantilever, as it was pushed into the sample surface, as a function of the displacement of the cantilever in the vertical direction. A minimum of eight indents was carried out on each sample. Indents were separated by at least 500 nm along the sample surface to ensure that each new indent would deform a previously unaffected area of the film.

Results

AFM images were taken of the topography of the films deposited on glass slides. Tapping mode images were taken over scan areas of 1×1 μm², 4×4 μm² and 10×10 μm² and are shown in FIGS. 8(a)-(c).

FIG. 8(a) reveals detail about the surface structure of Eudragit RS PO without plasticizer. Structures with heights of approximately 1-2 nm repeat over the surface with widths of 20 to 100 nm. Eudragit polymer films incorporating TEC show structures smaller in height (order of 0.1 nm) and shorter in width (order of 10 nm). The overall effect is that the film appears smoother, as shown in FIG. 8(b).

The addition of MCT changes the topography of the polymer films drastically. In the topographical image of Eudragit RS PO with 20% MCT, FIG. 8(c), structures can be seen which appear to dip in to the sample surface. Under the imaging conditions used, the structures observed, called inclusions, range from 0.5 to 1 μm in diameter and 10 to 20 nm in depth.

To determine the nature of the inclusions observed in the Eudragit RS PO polymer film, the AFM cantilever can be oscillated in tapping mode at greater amplitudes. The force that the AFM taps the sample surface with every oscillation is dependent on the amplitude of oscillation. With a higher oscillation amplitude, a greater force is applied to the sample surface by the AFM probe tip.

The contrast of images shown in FIGS. 8(d) (i) to (iii) increases with greater force applied to the sample surface. Therefore, the depth of the inclusions observed increases with greater tapping mode force. This information shows that the inclusions observed are not empty “pores”, but are filled with a material that is softer than the surrounding areas. This material is deformed more than the surrounding areas when a greater force is applied by the AFM probe tip.

Example 9 Atomic Force Microscopy Imaging of a Film-Forming Composition of Example 2

Glass substrates with a layer of the film-forming composition 06P of Example 2 were prepared and the surface structure imaged. The polymer films were spin coated on glass substrates and subsequently imaged using atomic force microscopy (AFM). 10 droplets were put on the substrate while it was spinning slowly for the first 10 seconds. Spincoating was carried out at 5000 rpm for 40 sec with a 500 rpm/s acceleration. Atomic force microscopy (AFM) gives a direct image of the surface structure by raster scanning a sharp tip over the surface with a non-destructive force. It gives the height h(x,y) as a function of the x and y position on the surface. The AFM used is a metrology AFM specifically designed to measure accurately. The tip is moved vertically over the sample surface while the sample is scanned horizontally using piezoelectric flexures equipped with strain gauge distance sensors. All measurements were carried out in intermittent contact mode using single crystal silicon cantilevers with spring constants of approximately 40 Nm and radius of curvature of 5 nm to 10 nm according to the manufacturer. The height is calibrated with a grating traceable to recognised international standards.

AFM used: The AFM used is a NX20 Atomic Force Microscope from Park System Corp.

Image Processing

To best display and analyse the results the images were line wise corrected by subtracting a first order least mean squares fit in order to remove tilt of the sample relative to the scanning probe. The images are displayed as two-dimensional maps with and overlaid colour scale ranging from white (top) to black (bottom). The colour scale is displayed to the right of the images with a scale in nm or μm.

Roughness: The roughness is a measure of the vertical deviation of the real surface from its ideal flat form and is calculated for the recorded images. The arithmetical deviation of the assed profiles in the images is calculated and stated as an estimate of the roughness value R_(a). It is calculated as:

$\left( {R_{a} = \sqrt{\frac{1}{mn}{\sum\limits_{j = 1}^{m}{\sum\limits_{i = 1}^{n}\; {{h\left( {x_{i},y_{j}} \right)}}}}}} \right)$

Where m is the number of lines in the image and n is the number of point sampled over a line.

For information the raw image is included in the bottom of the figures.

Software used: The software used for image processing is SPIP form Image Metrology.

Measurement Uncertainty

The measured surface profile includes possible contamination or particles adsorbed to the surface. Let h be the observed height of a protruding bump or hill measured relative to a baseline. For a clean surface the standard uncertainty u at a confidence level of 68% is estimated to be

u(h)≈1 nm+0.02·h

This estimate contains contributions from the calibration method, from the reference standards used and from the environmental conditions. The longterm characteristic of the object measured is not included. For comparison the standard measurement uncertainty u of a step height h_(step) of h_(step)=20 nm is u(h_(step))=1.1 nm.

The calculated roughness R_(a) is only valid for the area measured. For a clean surface the standard uncertainty u at a confidence level of 68% is estimated to be

u(R_(a))≈5 nm+0.2 ·R_(a)

This estimate contains contributions from the calibration method, from the reference standards used and from the environmental conditions. The longterm characteristic of the object measured is not included.

Results

As shown in FIG. 9, the surface of the film-forming composition exhibits a porous surface structure with holes—or valleys—with depths from a few nanometres to several hundred nanometres. The diameters of the pores range from approximately hundred nanometres to more than one micrometres. Thus, it appears that a film-forming composition containing both a plasticizer and an oily release-enhancing agent has a similar topography to a film-forming composition containing the oily release-enhancing agent without a plasticizer, and that the holes identified by AFM are not empty but filled with droplets of the oily release-enhancing agent. 

What is claimed is:
 1. A film-forming pharmaceutical composition for dermal application, the composition comprising at least one therapeutically active ingredient dissolved in a pharmaceutically acceptable volatile solvent which is present in an amount of 50-99.5% w/w of the composition, the composition further comprising a film-forming polymer in an amount of 0.1-50% w/w, a plasticizer in an amount of 0.1-10% w/w, and medium chain triglycerides as an oily release-enhancing agent in an amount of 0.1-15% w/w; the composition being capable of forming, after application on skin and evaporation of the solvent, a continuous phase comprising the film-forming polymer and the plasticizer and a dispersed phase comprising droplets of medium chain triglycerides.
 2. A composition according to claim 1, wherein the film-forming polymer is selected from the group consisting of cellulose derivatives, acrylic polymers, acrylic copolymers, methacrylate polymers, methacrylate copolymers, polyurethanes, polyvinylalcohol or a derivative thereof such as polyvinylacetate, silicone polymers and silicone copolymers, or copolymers thereof.
 3. A composition according to claim 2, wherein the cellulose derivative is selected from the group consisting of ethyl cellulose, methyl cellulose, hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropylmethyl cellulose.
 4. A composition according to claim 2, wherein the acrylic polymer is selected from the group consisting of methyl methacrylate and butyl methacrylate copolymer, ethyl acrylate and methyl methacrylate copolymer, acrylate and ammonium methacrylate copolymer type A and type B, and acrylates/octylacrylamide copolymer.
 5. A composition according to claim 1, wherein the amount of film-forming polymer is 5-20% w/w.
 6. A composition according to claim 1, wherein the plasticizer is selected from the group consisting of triethyl citrate, tributyl citrate, acetyl triethyl citrate, triacetin, dibutyl sebacate and polyethylene glycol 100-1000.
 7. A composition according to claim 1, wherein the amount of plasticizer is 2-5% w/w.
 8. A composition according to claim 1, wherein the amount of medium chain triglycerides is 1-10% w/w.
 9. A composition according to claim 1, wherein the volatile solvent is a lower alcohol such as methanol, ethanol, n-propanol, isopropanol or butanol, a C₁₋₄ ester of a C₁₋₄ carboxylic acid such as methyl acetate, ethyl acetate, butyl acetate, methyl formate or propyl propionate, acetone, or a volatile silicone oil such as cyclomethicone, dimethicone or hexamethyldisiloxane.
 10. A composition according to claim 1, wherein the amount of the volatile solvent is 70-80% w/w or 80-90% w/w.
 11. A composition according to claim 1 further comprising an anti-nucleating agent.
 12. A composition according to claim 11, wherein the anti-nucleating agent is selected from the group consisting of polyvinyl alcohol, hydroxypropyl cellulose, hydroxypropylmethyl cellulose, methyl cellulose, polyvinylpyrrolidone and carboxymethyl cellulose.
 13. A composition according to claim 1 which is substantially anhydrous.
 14. A composition according to claim 1, wherein the therapeutically active ingredient is selected from the group consisting of vitamin D derivatives or analogues, corticosteroids, phosphodiesterase 4 inhibitors, ingenol derivatives, retinoids, MK inhibitors, NK-1 receptor antagonists, calcineurin inhibitors, keratolytic agents, antibiotics, non-steroidal antiinflammatory agents and local anesthetics.
 15. A method of treating a dermatological disease or condition, the method comprising applying a composition of claim 1 on the skin of a patient in need such treatment.
 16. The method of claim 15, wherein the dermatological disease or condition is selected from the group consisting of psoriasis, pustulosis palmoplantaris, ichtyosis, atopic dermatitis, contact dermatitis, eczema, actinic keratosis, pruritus, rosacea and acne.
 17. A composition according to claim 4, wherein the acrylic polymer is ethyl acrylate and methyl methacrylate copolymer.
 18. A composition according to claim 5, wherein the amount of film-forming polymer is 10-15% w/w.
 19. A composition according to claim 6, wherein the plasticizer is tributyl citrate.
 20. A composition according to claim 8, wherein the amount of medium chain triglycerides is 2-6% w/w. 